The present invention deals with power machines. More specifically, the present invention deals with an electronic clock for use as an hour meter in a power machine.
Power machines, such as skid steer loaders and mini-excavators, often require maintenance which is performed based on a number of hours of operation of the power machine. The number of hours of operation can give maintenance personnel an idea of what parts might be wearing, and what maintenance operations should be considered and performed.
Such power machines often operate in fairly hostile conditions. In other words, the power machines are often operated at construction sites over various extremely rugged terrains, and in environments which are filled with dust, snow, mud and other debris. Similarly, such power machines can operate in electronically noisy environments where electronic signaling encounters difficulty.
In spite of these difficult operating conditions, it is still desirable to maintain the hour meter for the power machine (i.e. the electronic clock) with a high degree of accuracy. Therefore, in prior systems, the hour meter was implemented with an electronic controller and a timing circuit. The actual hour meter value was stored at three separate locations in memory. At predetermined intervals, the controller would write an updated hour meter value to all three locations in memory. The write operations were performed substantially simultaneously. While this system did substantially improve the accuracy by reducing problems associated with bad memory locations and by reducing the problems associated with single bad memory write operations, the system still had disadvantages.
For instance, if the hour meter data being written by the controller was somehow corrupted, this corrupted data would be written to all three memory locations such that all three locations would then contain corrupted data. Similarly, the prior clocks wrote to all three memory locations upon power-up and power-down. However, due to different circuits in the control system powering down at different times, and glitches which can occur on signal and power lines during power-down, the hour meter value at power-down can be inaccurate. Therefore, again, all three memory locations would be written with inaccurate data.
A clock stores time data indicative of time of operation of a power machine. A timing circuit provides a timing signal and a controller is coupled to a timing circuit and to a memory, which includes a plurality of memory locations. An elapsed time value is maintained, based on the timing signal, by the timing circuit, and a subset of a plurality of memory locations is intermittently updated with the elapsed time value.